Dr. Keating's laboratory has defined genes contributing to arrhythmia susceptibility. He first focused on the long QT syndrome and idiopathic ventricular fibrillation, both inherited disorders that cause sudden death from episodic ventricular tachyarrhythmias. Over the last few years, Dr. Keating has discovered all of the known arrhythmia susceptibility genes, and has provided the first molecular insights into the pathogenesis of cardiac arrhythmias. His studies are now expanding into the molecular genetics of dilated cardiomyopathy, and his genetic analytic approach has already localized genes causing this disorder. Key to the success of these studies has been the identification of co-segregation of a phenotype with a genotype in specific, informative families. Accurate phenotyping is essential to gene mapping and cloning using the linkage approach. Dr. Keating makes extensive use of the GCRC Core Laboratories for his studies. Phenotyping of key family members may be carried out in the inpatient unit, but most often, phenotyping is done by Dr. Keating and other members of the Division of Cardiology in the Cardiology Outpatient Clinics. Blood samples are then drawn and forwarded to the Core Laboratory. When study subjects have blood drawn on the GCRC, visits are not recorded, as they are brief and only for the purpose of drawing blood. With Dr. Keating's expanded interests in cardiomyopathies, he projects a greatly increased utilization of the GCRC clinical unit for the required phenotyping studies. Dr. Keating has been a very productive Center investigator, and has published nine papers in the last year describing his work.